Simple mathematical question

[Kai-Roger]

I have no idea, but maybe this will work

A = grp.getvalue('6/6/1')
B = grp.getvalue('6/6/2')
C = grp.getvalue('6/6/4')
D = math.round((B - A) / (C - A) *100, 2)
grp.write('6/6/10', D)

Hi.
Thanks for the reply. I sort of found it out in the meanwhile (:

A = grp.getvalue ('6/6/1') --Temp before the heat-recovery (outside temp)
B = grp.getvalue ('6/6/2') --Temp after the heat-recovery
C = grp.getvalue ('6/6/4') --Return temp from house (before the heat-recovery)
D = grp.find ('6/6/10') -- Efficiency heat-recovery

D :write(((B-A)/(C-A))*100)

Now i get the efficiency in % of my "rotating heat recovery unit" in my "house ventilation" (: